(1) Field of the Invention
This invention relates to an automatic reverse mechanism for a tape recorder. When the rotation of reel shafts is stopped, the automatic reverse mechanism detects it and switches the actuated pinch roller from a left-hand pinch roller to a right-hand pinch roller and vice versa.
(2) Description of the Prior Art
As automatic reverse mechanisms for tape recorders, there have heretofore been known those detecting electrically each end of a magnetic tape and actuating an electromagnetic plunger so as to switch the actuated pinch roller from a left-hand pinch roller to a right-hand pinch roller and vice versa; and those detecting mechanically a tensile force indicative of each end of a magnetic tape so as to switch the actuate pinch roller from a left-hand pinch roller to a right-hand pinch roller and vice versa by making use of the rotary power of a flywheel or the like.
However, the former automatic reverse mechanisms are equipped respectively with electromagnetic plungers and hence have complex structures. They are accordingly disadvantageous for dimensional reduction. The latter automatic reverse mechanisms generally have such a structure that a pin is provided upright on a flywheel and a pinch roller changeover mechanism is triggered by the pin. This structure is however accompanied by a potential danger that the balance of the flywheel would be impaired. It also involves another potential danger that the mechanism could malfunction as a result of detection of a tentative increase of the tape tension at the time of start.
FIGS. 4 and 5 illustrate an automatic reverse mechanism for a tape recorder, which has solved such problems. An application for patent has already been filed thereon by the present assignee (Japanese patent application No. 192835/1983).
FIG. 4 illustrates the automatic reverse mechanism with a right-hand reel shaft 1a being in rotation, while FIG. 5 illustrates the same automatic reverse mechanism in the course of its change from the state shown in FIG. 4 to another state in which a left-hand reel shaft 1b is rotated.
Referring first of all to FIG. 4, capstans 3a,3b, pinch rollers 4a,4b and the above-mentioned reel shafts 1a,1b are disposed respectively in a symmetrical relation. Small diameter gears 5a,5b and flywheels 6a,6b are respectively secured on the capstans 3a,3b. There are also provided turnable members 7a,7b turnably about their corresponding capstans 3a,3b. Rotation transmitting units composed in combination of large diameter gears 8a,8b and small diameter gears 9a,9b respectively are supported on one ends of the turnable members 7a,7b via shafts 10a,10b. Eccentric circular cam surfaces 11a,11b are formed respectively about the shafts 10a,10b. In addition, pushing projections 12a,12b are also provided integrally with the shafts 10a,10b at positions where the eccentric cam surfaces 11a,11b have the maximum radii. On the other hand, the other ends of the turnable members 7a,7b terminate in bent end portions 13a,13b.
The pinch rollers 4a,4b are supported on brackets 15a,15b, which are pivotal about pivots 14a,14b respectively, so that the pinch rollers 4a,4b can be releasably brought into contact with their corresponding capstans 3a,3b. Bent edge portions 16a,16b are also provided on the respective brackets 15a,15b.
A changeover bar 17, which is slidable horizontally as viewed in FIG. 4, is provided with lugs 18a,18b;19a,19b in such a way that the bent end portions 13a,13b of the respective turnable members 7a,7b are interposed between the corresponding lugs 18a,19a and 18b,19b. The changeover bar 17 also defines openings 20a,20b which receive the bent edge portions 16a,16b of the brackets 15a,15b respectively. Tilted edges 21a,21b are formed by parts of the openings 20a,20b. When the changeover bar 17 moves rightwards, the left-hand tilted edge 21b is caused to slide on the bent edge portion 16b of the left-hand bracket 15b as illustrated in FIG. 4, whereby the left-hand pinch roller 4b is separated from its corresponding capstan 3b. When the changeover bar 17 moves leftwards, the right-hand tilted edge 21a is caused to slide on the bent edge portion 16a of the right-hand bracket 15a, whereby the right-hand pinch roller 4a is separated from its corresponding capstan 3a. However, the respective brackets 15a,15b are biased by their corresponding unillustrated springs in such directions that the respective pinch rollers 4a,4b are pressed against their corresponding capstans 3a,3b.
Further, a two-state switch lever 25 which is pivotal in a two-state fashion between paired stopper pins 23 and 24 by a toggle spring 22 is provided in the vicinity of one end of the changeover bar 17. These two-state switch lever 25 and toggle spring 22 constitute a pinch roller changeover mechanism together with the changeover bar 17. When the changeover bar 17 has moved, for example, in the leftward direction and the two-state switch lever 25 has been turned to a point beyond the neutral point, the changeover bar 17 is moved further in the leftward direction owing to the turning force of the two-state switch lever 25, whereby the right-hand pinch roller 4a is separated from the associated capstan 3a.
Of the large diameter gears 8a,8b and small diameter gears 9a,9b which in combination constitute the rotation transmitting units, the large diameter gears 8a,8b are maintained in meshing engagement with the small diameter gears 5a,5b provided as unitary members with the capstans 3a,3b respectively, while the small diameter gears 9a,9b are selectively engageable with large diameter gears 26a,26b provided coaxially with the reel shafts 1a,1b. By the way, the meshing engagement between the gears 9a and 26a and that between the gears 9b and 26b are controlled respectively by the turning movements of the turnable members 7a,7b. Both turnable members 7a,7b are however biased by their corresponding tension springs 27a,27b in such directions that the gears 9a,9b are brought into meshing engagement with their corresponding gears 26a,26b. On the other hand, the turning movements of the turnable members 7 a,7b are controlled by the horizontal movement of the changeover bar 17. The turnable member 7a,7b and changeover bar 17 are linked together in such a way that while one of the gears (for example, the right-hand gear 9a) is maintained in meshing engagement with the gear 26a, the other gear 9b is maintained out of engagement from the gear 26b.
Mounted on the reel shafts 1a,1b are rotary members 28a,28b which rotate together with their corresponding reel shafts 1a,1b. Pin-like pushing and urging portions 29a,29b are fixedly provided on the rotary members 28a,28b respectively. Friction mechanisms (not shown) are interposed between the reel shafts 1a,1b and the rotary members 28a,28b and between the reel shafts 1a,1b and the large diameter gears 26a,26b respectively. For example, the large diameter gear 26a can still be allowed to rotate even after the rotation of the reel shaft 1a has been stopped. In this case, the corresponding friction mechanism undergoes slipping. The friction mechanism described in copending U.S. patent application Ser. No. 927,184 filed on Nov. 5, 1986 and assigned commonly to the present assignee, which is incorporated herein by way of reference, may be suitably used as the above friction mechanisms. Designated at numeral 30 is a fixing plate, on which cam followers 31a,31b and auxiliary holding members 32a,32b are pivotally supported.
The cam followers 31a,31b have contact portions 33a,33b at locations farthest from their fulcrums, pressure receiving portions 34a,34b located respectively on the orbits of revolutions of the pushing and urging portions 29a,29b, and elastic fingers 35a,35b in the vicinity of the fulcrums. On the other hand, the auxiliary holding members 32a,32b have a substantially L-like configuration. Lower arms 36a,36b are located outside the shafts 10a,10b, while upper arms 37a,37b are positioned in opposition to the elastic fingers 35a,35b of the cam followers 31a,31b.
The operation will next be described. In FIG. 4, the right-hand pinch roller 4a is in contact under pressure with the capstan 3a and the rotation of the capstan 3a, the direction of which is indicated by an arrow, is being transmitted via the gears 5a,8a,9a,26a and the unillustrated friction mechanism to the right-hand reel shaft 1a. At this time, the rotary power of the reel shaft 1a is being transmitted to the cam follower 31a by way of the pushing and urging portion 29a, whereby the contact portion 33a of the cam follower 31a is maintained in sliding contact with the cam surface 11a. So long as the contact portion 33a is maintained in sliding contact with the cam surface 11a in the above-described manner, the contact portions 33a is maintained out of contact with the pushing projection 12a.
Let's now assume that either playback or recording operation is being performed while a magnetic tape (not shown) is being taken up on the right-hand reel shaft 1a. Since the left-hand reel shaft 1b serves as a tape-releasing side at this time, the pushing and urging portion 29b does not push the pressure-receiving portion 34b of the cam follower 31b. In this state, the left-hand rotation transmitting unit (gears 8b,9b) has however been separated from the large diameter gear 26b to a non-engagement position relative to the reel shaft 1b. Accordingly, the lower arm 36b of the auxiliary holding member 32b is being pushed by the shaft 10b. As a result, the upper arm 37b of the auxiliary holding member 32b is pressing the elastic finger 35b of the cam follower 31b so that the auxiliary holding member 32b in place of the pushing and urging portion 29b maintains the contact portion 33b of the cam follower 31b in sliding contact with the cam surface 11b.
When the tape has been fully wound up on the right-hand reel (not shown), slipping is developed in the friction mechanism interposed between the large diameter gear 26a and the reel shaft 1a so that the reel shaft 1a stops. The contact portion 33a which has been kept in sliding contact with the cam surface 11a is hence separated from the cam surface 11a at a location where the contact portion 33a is closest to the shaft 10a and as illustrated in FIG. 5, the pushing and urging portion 12a is brought into contact with the contact portion 33a. Since the fulcrum of the cam follower 31a does not move, the rotation transmitting member, namely, the turnable member 7a is hence caused to turn against the force of the spring 27a so that the gear 9a is separated from the large diameter gear 26a. As a result, the transmission of the rotary power to the large diameter gear 26a is stopped.
On the other hand, a turning movement of the turnable member 7a causes the bent end portion 13a thereof to press the lug 19a of the changeover bar 17 from the right as shown in FIG. 5, thereby moving the changeover bar 17 leftwards. In response to the leftward movement of the changeover bar 17, the two-state switch lever 25 is caused to turn clockwise while compressing the toggle spring 22. As soon as the toggle spring 22 is moved beyond the neutral point, the spring force of the spring 22 acts in the direction that the two-state switch lever 25 is turned further in the clockwise direction. Hence, the changeover bar 17 is caused to move rapidly in the leftward direction.
Here, the left-hand inclined edge 21b of the change-over bar 17 releases the bracket 15b. In contrast, the right-hand inclined edge 21a causes the bracket 15a to turn in a direction opposite to its biased direction. As a result, the left-hand pinch roller 4b is brought into contact under pressure with the capstan 3b while the right-hand pinch roller 4a is separated from the capstan 3a. Further, the left-hand turnable member 7b is pulled by the spring 27b and is hence caused to turn clockwise, whereby the small diameter gear 9b is brought into meshing engagement with the large diameter gear 26b in the same rotation transmitting unit. In the above state, opposite to the state shown in FIG. 4, the left-hand reel shaft 1b is caused to rotate in the winding direction and a playback or recording operation is performed while the tape is being wound up on the left-hand reel.
According to a structure such as that described above, accessory parts such as electromagnetic plungers are not required so that the size reduction of an automatic reverse mechanism is facilitated. The above automatic reverse mechanism has such additional advantages that it does not impair the balanced rotation of the flywheels and owing to the actuation of the pinch roller changeover mechanism upon detection of each stop of the reel shafts, it is free from malfunction even if the tape tension is increased temporarily at start.
In the above-described automatic reverse mechanism, the rotary powers of the reel shafts 1a,1b are however transmitted to their corresponding cam followers 31a,31b by way of the unillustrated friction mechanisms, rotary members 28a,28b and pushing and urging portions 29a,29b. Accordingly, the rotary powers are lost significantly during their transmission from the reel shafts 1a,1b to the cam followers 31a,31b. In order to reduce their losses in the course of their transmission, the friction forces between the reel shafts 1a,1b and the corresponding rotary members 28a,28b have been set at a high level. Since the friction forces act as a back tension at the tape-feeding side (releasing side), they have created a problem that a greater difference arises between the running speed of a magnetic tape at the start of its winding and the running speed of the magnetic tape at the end of its winding due to the change in the diameter of the tape taken up on the tape winding side.
The above automatic reverse mechanism involves another problem that it requires many parts, since the rotary members 28a,28b are interposed between their corresponding reel shafts 1a,1b and cam followers 31a,31b, and the auxiliary holding members 32a,32b are provided as parts discrete from the cam followers 31a,31b in order to maintain the contact portion 33a or 33b of the cam follower 31a or 31b on the feeding side during takeup of a magnetic tape (i.e., the cam follower 31b in FIG. 4) in contact with the its corresponding cam surface 11a or 11b.